FYI push button start via relay, on my second Optima Red battery. My motor will only turn over with a full charge. If it is drained at all, when the start button is pressed, voltage drops to 10 and nothing happens. Doesnt even try to turn over. If it is fully charged or hooked up to charger it works. During a race I am only getting 12.5-13 volts, sometimes 13.5 on a good day (however, i am running fans and coolshirt). I am wondering the following:

Is it the alternator or voltage regulator? If so, it shouldn’t have anything to do with not starting i wouldn’t think

Is it the battery? It’s AGM so it wants a higher charge voltage that it’s not getting. Is there a 14.5-7 voltage regulator out there?

Is it the starter? Works totally fine when it turns over. Doesn’t even try when it is not

Is it the relay on the start button? If voltage is dropping to 10, would that be a reason that the relay many not send a start signal to starter? I hear the relay clicking when button is pressed.

I had a very similar problem. Ended up being the ignition toggle switch which powered the start button. I believe it degraded over time due to the high start current draw. Try to start the car with the Diagnostic Connector. If the starter turns over easily under reduced charge states, mine did, then the problem is in the control side.

check any for any loose connections, I had a similar problem and it was a loose connection at the starter. it felt tight but it wasn’t bottomed out. also we have had no luck with the Red tops, don’t last long at all.